Self-monitoring has an important limitation, which is that people can only self-monitor processes and things that they are capable of paying attention to. It is easily possible to monitor external behaviors such as checking behavior (e.g., how many times you run back to your doorstep to check to see if your door is indeed locked). It is much harder, if not impossible to monitor internal behaviors, such as how fast your heart might be beating, or whether you are sweating or not. These sorts of internal processes are nevertheless important to be able to monitor, because they are symptoms of anxiety, which might be exactly something you are wanting to rid yourself of having to deal with. Heart rate increases when you are afraid, for instance, and people tend to sweat more too.
Internal body processes such as heart rate and sweating can be rather easily monitored, it turns out, with the aide of special biofeedback equipment; machines that have been designed to pick up on subtle body signals and provide you with feedback as to how those signals are progressing. Generally, some sort of sensor is hooked from the machine to your body, and the machine then records the signals from this sensor, and feeds them back to you visually or by making sounds. So, a biofeedback heart rate monitor might make a sound every time your heart beats, increasing the frequency of that sound when your heart beats faster, and decreasing the frequency of that sound when your heart beats slower. The same information can be presented in the form of a moving visual graph, or as an instantaneous measurement score.

You have used biofeedback equipment if you have ever squeezed the handles of exercise equipment in order to let the machine measure your heart rate. You have also used biofeedback equipment if you have ever been in the hospital and they have hooked you up to heart rate or other body monitors. Though these machines used to be very expensive and only available to professionals, advances in computers and electronics have made them more widely available such that individuals can purchase personal units today.
Just as biofeedback can be used to teach people how to relax efficiently, it can also be used to help people unlearn problem behavior, including anxiety behaviors. When incorporated into Systematic Desensitization, for instance, biofeedback can be substituted for the normal relaxation exercises that form a part of that procedure. As systematic desensitization is discussed in detail elsewhere in this document (link to discussion of Systematic Desensitization, below), we’ll not elaborate here.

Neurofeedback is a variation on biofeedback. Where biofeedback involves measurement of body signals, neurofeedback involves measurement of the brain. The most common forms of neurofeedback uses head-mounted electrodes to measure brain waves; the massed electrical output of the brain’s millions of neurons. These waves change as consciousness changes. The presence of different waveforms lets people know when someone is sleeping or awake, and when they are concentrating or letting their attention drift. No surgery is involved, we should note! These electrodes are strictly the surface-mounted variety, often with a sticky contact paste or adhesives to hold them in place, or alternatively, arrayed inside a “bathing cap” sort of headgear.
Neurofeedback techniques have shown promise for helping people learn to concentrate better; a skill of particular interest to people dealing with learning disorders and ADHD. Various neurofeedback products are available for the home and professional market.

Source: Centersite.net